1. Field of the Invention
The present invention relates generally to filtration apparatus for use in the fields for example of semiconductor, foods and chemicals and more specifically to highly durable filtration apparatus ensuring precision filtration and in addition dispensing with an O ring used for a sealing portion for attaching a housing bowl.
2. Description of the Background Art
In a variety of fields manufacturing electronic components, foods, chemicals, pure water and the like, filtration apparatus are widely used to provide precision filtration. Electronic components are washed with agents having high levels of purity. For example if such an agent is contaminated for example with metal particles in particular and it is used to wash micro-fabricated semiconductor integrated circuits, the circuits would have interconnections with short-circuit or the like introduced therebetween and they would not be expected to function normally. On the other hand for example agents employed to wash products in semiconductor fabrication can be used repeatedly and in terms of resource conservation, environmentalism and reduction of semiconductor device fabrication cost the washing agent is circulated and reused. In doing so, metal particles and the like are introduced during the process of washing and agent recovery, as described above, and the contaminant is removed with a filter. The filter, initially clean, is contaminated in use by non-filtrate over time and clogged in time and eventually can no longer provide sufficient filtration. Thus the filtration apparatus described above employs a filter having filtration capability dropping to a predetermined level over a period of time and when the period of time elapses the filter is exchanged with a new filter. Whenever filters are exchanged, the filtration apparatus is unsealed and disassembled to exchange the cartridge filter.
FIG. 12 illustrates a conventional filtration apparatus including a housing head 110 having an inlet 114 and an outlet 115, a cartridge 101 detachably attached to the housing head, and a housing bowl 111 surrounding the cartridge to define a channel wall. Housing head 110 and housing bowl 111 cooperate to form a housing 113. A filter attachment 108 with an O ring 121 fitted thereon is fitted into a filter attachment 125 in the housing head to allow cartridge filter 101 to provide a seal and also be detachably attached. Housing bowl 111 has an upper end provided with an O ring recess 131 receiving an O ring 122 which abuts against a flange 132 protruding from the housing head downward and a cap nut 112 is screwed to clamp it. Thus, the O ring and an end of the flange pushes each other to provide a seal. In other words, the apparatus is sealed between O ring 122 and flange 132. The housing head has an air vent and a pressure gauge connection 116, 117, 118 and housing bowl 111 has an effluent port 119.
Inlet 114 introduces a fluid to be filtered, and as it passes through cartridge filter 101 the fluid is filtrated therethrough and it then passes through filter attachment 125 and finally it is output through outlet 115.
For the filtration apparatus as described above, however, when cartridge filter 101 is exchanged, O ring 122 providing a seal is conventionally also exchanged to thoroughly prevent introduction of particles. For example, O ring 122 formed of a simple substance of fluororubber is extremely expensive and if an O ring has an internal portion of rubber and an external portion of fluororesin the cost still would be relatively high. Exchanging such an expensive O ring whenever a cartridge filter is exchanged is not preferable as such would impair cost-competitiveness. Furthermore, it is neither preferable ecologically as it increases refuse. Furthermore, if the O ring is not formed of fluororubber, the exact O ring can act as a contaminant introducing particles or other foreign matters. Thus there has been a demand for a filtration apparatus developed to have a sealing structure free from frequent exchange of an O ring providing a seal between a housing head and a housing bowl, or dispensing with such exchange.